Co0.9Fe0.1薄膜面内元素分辨的磁各向异性

利用X射线磁性圆二色技术对Co_0.9Fe_0.1薄膜面内元素分辨的磁各向异性进行了研究，通过剩磁模式测量不同磁化方向的样品组分原子单位空穴磁矩的变化，发现除了在生长的磁诱导方向存在易磁化轴外，在与该轴垂直的方向还存在一个类似易轴的软磁化轴；面内的两个难磁化轴与易磁化轴取向大约成66°夹角，从而构成了面内双轴磁各向异性；对不同组分元素，其单位空穴磁矩随磁化方向的变化趋势基本相同，不同磁化方向Fe原子单位空穴的磁矩值约为Co的对应值的87%，反映了Fe原子和Co原子之间存在着强烈的铁磁性耦合. 关键词： 磁各向异性 X射线磁性圆二色 铁磁耦合 CoFe合金薄膜     

磁性纳米线反磁化过程的截椭球链模型

依据实际的纳米线形貌，提出了描述磁性纳米线反磁化过程的截椭球链模型.基于此模型，推导了纳米线反磁化过程中不可逆磁化的临界场和矫顽力在一致转动和对称扇形模式下的表达式.同时，还研究了椭球间接触角、单轴磁晶各向异性、外场与链轴方向夹角、截椭球个数和椭球形状因子对临界场和矫顽力的影响.利用该模型解释了镍纳米线的反磁化过程可能是对称扇形的模式. 关键词： 截椭球链模型 反磁化 一致转动 对称扇形     

铁磁共振实验中值得注意的几个问题

与顺磁样品相比铁磁样品的磁共振信号不仅是强得多,铁磁样品的许多特点都会在铁磁共振(FMR)谱中反映出来.诸如,起始磁化过程的FMR谱线与有剩余磁化强度Mr的FMR谱是不同的,起始磁化过程中的巴克豪森跳跃也会在FMR谱中反映出来.样品的磁晶各向异性、形状各向异性,铁磁高温顺磁的磁性相变等等都能用FMR方法加以研究.     

Co0.9Fe0.1薄膜面内元素分辨的磁各向异性

利用X射线磁性圆二色技术对Co0.9Fe0.1薄膜面内元素分辨的磁各向异性进行了研究,通过剩磁模式测量不同磁化方向的样品组分原子单位空穴磁矩的变化,发现除了在生长的磁诱导方向存在易磁化轴外,在与该轴垂直的方向还存在一个类似易轴的软磁化轴;面内的两个难磁化轴与易磁化轴取向大约成66°夹角,从而构成了面内双轴磁各向异性;对不同组分元素,其单位空穴磁矩随磁化方向的变化趋势基本相同,不同磁化方向Fe原子单位空穴的磁矩值约为Co的对应值的87%,反映了Fe原子和Co原子之间存在着强烈的铁磁性耦合.     

多能场复合电沉积对Al2O3-Co复合薄膜物性影响研究

采用多能场复合微细电沉积加工技术,制备了微观结构渐变的多彩结构色磁性Al₂O₃-Co复合薄膜.在沉积电场和与之垂直的偏转电场作用下,复合薄膜的微观结构、光学特性和磁性沿偏转电场方向呈现渐变特征.通过建立微观结构等效模型,理论分析了复合薄膜微观结构变化机理.通过软件仿真定量分析了沿偏转电场方向Co离子沉积电流密度分布规律,仿真结果与理论研究和实验结果相吻合.研究发现,采用多能场复合的微细电沉积加工技术可以从微观角度调控复合薄膜微区结构,实现对薄膜微区磁学和光学特性的精细调控.     

热处理对TbDyFe薄膜性能的影响

采用磁控溅射方法利用镶嵌靶材制备非晶TbDyFe薄膜,然后分别在150,300,450,550℃下退火,研究了热处理对TbDyFe薄膜性能的影响.结果显示,550℃温度下退火的样品出现RFe2相.随着退火温度的升高,晶粒逐渐长大,空洞网络变短而宽.薄膜的磁特性显示,其矫顽力及矩磁比均在出现RFe2相的550℃退火的样品中达到最大值.随着退火温度的增加,薄膜的易磁化轴从垂直膜面方向向平行膜面方向转动.     

钡铁氧体粒子反磁化研究

提出了钡铁氧体粒子反磁化的多扁椭球链模型,研究了形状各向异性、磁晶各向异性、层叠粒子数以及粒子间距对反磁化及其临界场、矫顽力的影响.此模型可用来解释取向钡铁氧体磁粉介质的反磁化机理. 关键词： 反磁化 多扁椭球链模型     

新型金属间化合物Sm(TiFe)_(12)的结构与磁性

SmTiFe_x(x的数值为8—11)可形成稳定的金属间化合物,经测定,晶体结构属于ThMn_(12)型四方结构,空间群为14/mmm,本文着重分析了Sm(TiFe)_(12)和Gd(TiFe)_12的结构和磁性。Sm(TiFe)_(12)具有很强的单轴磁晶各向异性,易磁化方向为c轴,居里温度610K。通过对Gd(TiFe)_(12)磁性的研究,进一步分析了在Sm(TiFe)_(12)中Sm和Fe次晶格的各向异性,实验结果表明,Sm和Fe次晶格都具有单轴磁晶各向异性,易磁化方向皆沿c轴。这是继Nd_2Fe_(14)B型永磁体以后发现的又一种具有单轴磁晶各向异性的三元稀土-铁金属间化合物。     

基于三维磁成像的近场磁性体探测

提出一种近场条件下未知磁源的三维磁成像方法.考虑到大多数磁性体不仅受背景磁场磁化,本身也带有较强剩磁,将观测面上的磁场转换为磁场矢量异常模量,并建立目标函数进行最优化求解,以得到符合观测磁场特征的磁性体磁化模型.仿真和实验表明：此方法可有效消除剩磁对反演结果的影响,能够实现对近场多个磁源磁化率分布的成像,验证了所提方法用于探测隐含磁体位置和形状的可行性.     

软x射线磁性圆二色吸收谱研究铁单晶薄膜的面内磁各向异性

利用软x射线磁性圆二色(XMCD)吸收谱测得Fe/MgO膜不同磁化方向的轨道磁矩和自旋磁矩.实 验表明，沿铁单晶薄膜的不同方向，铁原子轨道磁矩的改变量达到600%以上，而自旋磁矩的 变化约50%，但原子的总磁矩没有如此大的改变.结合常规方法分析了铁薄膜的宏观磁各向异 性性质，半定量地获得磁矩与宏观各向异性能的关系，并对样品的磁矩和磁各向异性能进行 了比较. 关键词： x射线磁性圆二色 磁各向异性 磁性薄膜     

Anisotropy and phase states of garnet ferrite films with misoriented surfaces

Anisotropy of garnet ferrite films is investigated in the framework of the two-parametric model. It is shown that a garnet ferrite film with an arbitrarily oriented surface is characterized by biaxial anisotropy. The directions of the easy, intermediate, and hard magnetization axes are determined as functions of the misorientation angle and weak cubic anisotropy. It is demonstrated that the region of existence of homogeneous states in a magnetic field is bounded by a slant astroid. The magnetic susceptibility tensor and the ferromagnetic resonance frequency are calculated, and the dispersion law of spin waves is determined.     

Spin reorientation transition in (111) textured L10 CoPt layers

In this work, a spin reorientation transition from [001] axis to an in-plane direction occurs near Curie temperature under a small external field for (111) textured L1₀ CoPt layers in an AlN/CoPt multilayer film, indicating the dominant role of the shape anisotropy at elevated temperatures over the magnetocrystalline anisotropy. A large in-plane residual magnetization is also observed after cooling the sample from a temperature above the Curie point. The formation of magnetization during cooling is considered due to the alignment of magnetic moments along the easy axis by the small field in the spin reorientation transition temperature region. Our work reveals the importance of shape anisotropy for the formation of magnetization in the heat assisted magnetic recording process.     

Epitaxial strain-induced magnetic anisotropy in Sm3Fe5O12 thin films grown by pulsed laser deposition

Sm₃Fe₅O₁₂ thin films of various thicknesses were grown on a (0 0 1)-oriented Gd₃Ga₅O₁₂ substrate by pulsed laser deposition. The crystal structure of the films was strongly dependent on film thickness. The lattice was strained for thinner films due to a lattice mismatch between the film and substrate. This lattice strain was relaxed when the film thickness exceeded a critical thickness of around 660 Å. It is suggested that the epitaxial strain induces uniaxial magnetic anisotropy with an out-of-plane magnetic easy axis.     

Asymmetrically shaped hysteresis loop in exchange-biased FeNi/FeMn film

The magnetization reversal of the bilayer polycrystalline FeNi(50 Å)/FeMn(50 Å) film sputtered in a magnetic field has been studied by magnetic and magneto-optical techniques. The external magnetic fields were applied along the easy or hard magnetization axis of the ferromagnetic permalloy layer. The asymmetry of hysteresis loop has been found. Appreciable asymmetry and the exchange bias were observed only in the field applied along the easy axis. The specific features of magnetization reversal were explained within the phenomenological model that involves high-order exchange anisotropy and misalignment of the easy axes of the antiferromagnetic and ferromagnetic layers. It has been shown that the film can exist in one of three equilibrium magnetic states in the field applied along the easy axis. The transitions between these states occur as first-order phase transitions. The observed hysteresis loop asymmetry is related to the existence of the metastable state.     

Preparation and FMR analysis of Co nanowires in alumina templates

Magnetic and structural properties of a high aspect ratio Co nanowire (NW) array electrodeposited in free-standing porous alumina template with a pore diameter of ∼200 nm are studied. Considered collectively, X-ray diffraction analysis, magnetometer and ferromagnetic resonance (FMR) measurements indicate that both the c-axis of crystal structure and the easy axis of magnetization are aligned preferentially perpendicular to the NW axis. The FMR spectra are characterized with very broad (a few kG) breadths and exhibit asymmetric shape in low field region due to under-saturation effects. Surprisingly, FMR spectra also revealed the presence of a spin-wave mode (SWM) as the applied field direction approached parallel to the film plane, i.e. perpendicular to the NWs. A brief discussion on this observation is provided. Further, characteristic magnetic parameters of the studied NW array were obtained by fitting the field angle-dependent FMR spectra and resonance field by using an analytical model that considers various factors affecting the total anisotropy.     

赝火花脉冲电子束传输中束斑分析

通过赝火花强流脉冲电子束对酸敏变色片和单晶硅的轰击试验，结合束流自箍缩效应进行理论计算，对赝火花脉冲电子束传输中束斑的变形进行了研究与分析. 结果表明椭圆形轰击束斑是由通过旁路电容的瞬态电流产生的方位角磁场所引起的，并且提出了解决束斑变形的有效方法. 关键词： 脉冲电子束 赝火花放电 束斑 自箍缩效应     

The modulated magnetic structure of α-Fe2O3: Ga weak ferromagnet

The domain structure of a diluted weak α-Fe₂O₃: Ga ferromagnet is considered. Magnetic fields of specific amplitudes and orientations applied in the basal plane of the crystal are found to produce nonuniform magnetic states due to a periodic deviation of the antiferromagnetic vector from the easy axis of crystallographic anisotropy. A phase diagram of the modulated magnetic state with the triad axis is constructed, and a dependence of the spatial period of modulation on an external magnetic field is studied. A phenomenological model and the nature of the magnetic superstructure discovered are discussed.     

磁场对模板法制备的Co纳米线结构和磁性的影响

在用二次氧化法制备的高度有序的氧化铝模板上通过交流电化学方法制备了Co纳米线阵列．研究了外加磁场及电解液pH值对纳米线生长的影响．在pH值为6.0和6.5的电解液中分别在不加磁场和沿纳米线轴向施加0.3 T磁场情况下制备了hcp结构的Co纳米线阵列．实验数据表明,沉积时外加磁场和调节pH值能有效影响纳米线中hcp结构的Co晶粒的易磁化轴沿纳米线长轴方向生长．由于晶粒的磁晶各向异性和纳米线沿长度方向的宏观形状各向异性叠加,制备的Co纳米线阵列具有高垂直各向异性,高矫顽力和较高矩形比． 关键词： Co纳米线阵列 织构 磁性     

Spin-engineering in the Co75Fe25/Cu(1 1 0) system

We present results on the growth and magnetic anisotropies of Co₇₅Fe₂₅ films grown on a Cu(1 1 0) single crystal. Angular dependent MOKE measurements show a thickness dependent, in-plane rotation of the easy axis of magnetisation of up to 60° from the [0 0 1] direction (towards [−1 1 0]). For a film thickness of 5 ML, just greater than that required for the onset of ferromagnetism, uniaxial anisotropy is observed with the easy axis along the [0 0 1] direction. As the film thickness increases this is seen to rotate in-plane towards the [−1 1 0] direction as the contribution from the cubic anisotropy constant grows. At a film thickness of 9 ML there is predominantly cubic anisotropy and at 10 ML the easy axis is rotated to 150° with respect to the [1 −1 0] axis, where it is stabilised.